1 Soil biology and system management Lisa M. Fultz Assistant Professor Soil Microbiology of Cropping Systems LSU AgCenter Baton Rouge, LA Award #: 2012-67019-30183
2 Ecosystem Functions from the Soil Perspective Physical Soil texture, compaction, PAW, aggregate stability Chemical ph, SOM, CEC, nutrients Biological Microbial biomass and activity, SOC, nutrient cycling, diseases
To Understand Soil Health We Must Understand Soil Biology 3 Plant growth enhancement Aggregate formation Water flow Nutrient cycling Water storage N fixation Plant protection Soil Biota Decompose residues Water filtration Pathogen supression Photo credit: Lisa M Fultz, LSU AgCenter Slide design: Jennifer Moore-Kucera, NRCS-SHD Detoxify pollutants Influence atmosphere composition
Soil Health Identifies the Importance of Soil Biology To Enhance Ecosystem Services 4 Increase amount, types and availability of plant residues. Minimize disturbance Increase #s and types of soil organisms Aggregate Stability OM Transformations Humus Formation Plant Growth, Productivity Resist erosion Increase H 2 O infiltration and storage Enhance water/air quality C sequestration Climate mitigation Biogeochemical Cycling Release plant available nutrients
5 Ecological Challenges to Soil Resilience Abiotic Variables: Depleted water sources Changes in precipitation patterns Extreme weather Erodibility indexes (>200 tons ha -1 y -1 ) Cultural Practices: High disturbance agronomic systems Intensive/ frequent tillage Low diversity Fallow periods Low residue return
6 Management Practices to Enhance Soil Health and Combat Soil Degradation Increase plant residues returned to the soil Perennial grasslands/forage lands Use crop rotations or cover crops Integrate cattle into cropping system Convert to conservation or no-till Enroll in conservation management programs
7 Integrated Crop-Livestock Agroecosystems Great flexibility Divide fields to suit needs/skill/resources Cotton Monocultures Grass-cattle Grain - Cotton Pullman clay loam soils ph = 7.4 SOM = 1.5 3.3% 34% clay
14 12 10 8 6 4 2 Fultz, L.M., Moore-Kucera, J., Zobeck, T.M., Acosta-Martinez, V, & Allen, V.G. (2013) 77:1659-1666. 1997 CTN_1 ICL_1 CTN_2 CTN_3 ICL_2 ICL_3 ICL_4 System 0 Soil organic C (g kg -1 ) Grassland 31% increase in SOC following 13 years under ICL management 8 Deficit irrigated continuous cotton Deficit irrigated bluestem & crop rotation Deficit irrigated continuous cotton Deficit irrigated continuous cotton Dryland forages & cotton Deficit irrigated perennial grasses Bluestem and fully irrigated row crops
9 Water use and productivity -Allen et al. 2012. Agronomy Journal Integrated system compared to continuous cotton Per hectare 25% less irrigation 36% less N fertilizer Decreased chemical inputs (pesticides and plant growth regulators) Avg. over 10 years profitability was similar when comparing the two systems
14 12 10 8 6 4 2 1997 CTN_1 ICL_1 CTN_2 CTN_3 ICL_2 ICL_3 ICL_4 System 0 Soil organic C (g kg -1 ) Grassland Deficit irrigated continuous cotton Deficit irrigated bluestem & crop rotation Deficit irrigated continuous cotton Deficit irrigated continuous cotton Dryland forages & cotton Deficit irrigated perennial grasses Bluestem and fully irrigated row crops ICL s increased aggregate stability 2-3x s that in continuous cotton 10
SOM and Aggregate Stability Mean weight diameter (mm) 0.80 0.60 0.40 0.20 0.00 Annual crops 11 Perennial Mean weight diameter (mm) 2.5 2.0 1.5 1.0 0.5 0.0 Relationship between increasing SOM and MWD (proxy for stability) Critical SOM value for enhanced aggregate stability Annual crops y = 0.04e 0.09x r² = 0.73*** Perennials 0 10 20 30 40 Soil organic matter (g kg -1 )
12 Mean weight diameter (mm) 2.5 0-5 cm Y= 0.05x + 0.24 r ² 0.357 2.0 r = 0.597 p < 0.0001 1.5 1.0 0.5 0.0 5-20 cm Y= 0.02x + 0.30 r ² 0.370 r = 0.608 p < 0.0001 0 5 10 15 20 25 30 35 40 Relative abundance of arbuscular mycorrhizal fungi (mol%)
13 What are the ecological impacts of increased fungal richness? Fungal operational taxonomic units (proportional to system area) Converting part or all of the field to rotation or perennial-based agroecosystems Increased Fungal Richness Increased SOM 1800 1600 1400 1200 1000 800 600 400 200 0 Fungal richness Diversity (diversity) Monoculture Cotton CTN_1 CTN_2 Rotations/ Perennial Systems FRG_CTN OWB_BER FRG_RC Monoculture Cotton Fungal richness (diversity) Rotations/ Perennial Systems Davinic, M. 2014, Ph.D. Dissertation
14 Available Soil P (ppm; Mehlich3) Do these shifts in microbial groups influence nutrient cycling? 250 200 150 100 50 Fungal Class Onygenales y = 27.467x + 38.791 R² = 0.248 Microbial composition influences the release of plant-available nutrients Bacterial Phylum Acidobacteria y = 16.852x + 2.4869 R² = 0.213 0 0.00 2.00 4.00 6.00 8.00 10.00 Relative abundance (%) Onygenales or Acidobacteria
15 Field Design Split plot design: Cover crop (CC) as main plot and N rates as sub plots 32 treatments: 8 cover crops and 4 N rates, with 4 reps for each CC*N treatment within a cover crop main plot N rates: 0, 235, 268, 302 kg Urea ha -1 Cereal radish + rye mix Radish (Raphanus sativus var. longipinnatus) Fallow Hairy vetch (Vicia villosa Roth) Crimson clover (Trifolium incarnatum L) Cereal rye (Secale cereale) Winter pea (Pisium sativum L) Berseem clover (Trifolium alexandrinum)
16 Cover crop dry weight biomass 3000 [CELLRANGE] 2500 Biomass weight (g) 2000 1500 1000 [CELLRANGE] [CELLRANGE] [CELLRANGE] [CELLRANGE] [CELLRANGE] [CELLRANGE] [CELLRANGE] 500 0 Fallow Berseem Clover Crimson Clover Hairy Vetch Winter Pea Cereal Rye Radish Rye+Radish
Soil organic matter 14.6% increase Fall 2014 to Fall 2015 17 2.4 [CELLRANGE] Soil Organic Matter (% LOI) 2.3 2.2 [CELLRANGE] [CELLRANGE] [CELLRANGE] [CELLRANGE] 2.1 Fallow Legume Grass Brassica Rye/Radish
18 C cycling enzyme greater in spring, fallowing cover crops 90 B-glucosidase (mg p-nitrophenol g-1 hr-1) 80 70 60 50 40 30 20 10 0 Fallow Legumes Grass Brassica Rye/Radish Fall 2014 Spring 2015 Fall 2015 Spring 2016
19 N cycling enzymes increasing over time 25 B-glucosaminidase (mg p-nitrophenol g-1 hr-1) 20 15 10 5 0 Fallow Legumes Grass Brassica Rye/Radish Fall 2014 Spring 2015 Fall 2015 Spring 2016
350 20 Total microbial biomass increased with SOM Total Microbial Biomass (nmol g -1 ) 300 250 200 150 100 50 y = 52.938x + 7.3273 R² = 0.2542 0 0 1 2 3 4 Soil Organic Matter (% LOI) 45 120 40 35 100 y = 0.2147x + 6.0442 R² = 0.1687 Nitrate-N (mg kg -1 ) 30 25 20 15 10 5 y = 0.1413x - 5.789 R² = 0.3082 Soil P (mg kg -1 ) 80 60 40 20 0 0 50 100 150 200 250 300 0 0 50 100 150 200 250 300 Total Microbial Biomass (nmol g -1 ) Total Microbial Biomass (nmol g -1 )
Fallow Berseem Crimson Hairy vetch Winter pea Cereal rye Radish Rye+Radish 21 76% 85% 77% 85% 82% 81% 75% 74% Fallow Berseem clover Crimson clover Hairy vetch Winter pea Cereal rye Radish Rye+Radish 64% 93% 123% 70% 132% 128% 67% 69%
r 3 Corn yields increased following sses and legumes 22 200 180 160 E BCD AB ABC A CD DE Corn grain yield (bu/a) 140 120 100 80 60 F 40 20
nter annuals overseeded on a perennial ture 23 uthern Mississippi ef cattle operation inter annual mixture Oats Triticale Annual ryegrass Hairy vetch Red clover Crimson clover White clover Turnip Radish
0 700 24 al pasture ded with r annuals Total Microbial Biomass (nmol g -1 ) 600 500 400 300 200 100 y = 57.9x - 23.55 R² = 0.4532 0 0 2 4 6 8 10 Soil Organic Matter (% LOI) y = 0.0839x + 7.4626 R² = 0.2816 90 80 70 y = 0.0552x + 7.8822 R² = 0.2939 Soil P (mg kg -1 ) 60 50 40 30 20 10
25 F, P, and 3
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27 Thank you! Lisa M. Fultz lfultz@agcenter.lsu.edu
28 arge macroaggregate roots Fibers
hat is the impact of ICLs on the ratio of ngi to bacteria (F:B)? Type of ratio impacts interpretation! 29 1 0.9 0.8 0.7 0.6 0.5 Highest F:B (18:2/Bac) ratio in continuous cotton Marker common for saprophytic fungi No change between ICLs 0.4 0.3 0.2 0.1
30 hat is the impact of ICLs on the ratio of ngi to bacteria (F:B)? 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Type of ratio impacts interpretation! AMF/Bac ratio: cotton < rotation < perennialbased systems
tive: Evaluate short-term soil health changes g conversion of CRP back to cropland CRP Converted to annual crops ems (CRP vs. Converted CRP) hs (0-10, 10-30, 30-50cm) s (2012, 2013, 2014) histories: ages 23-25 years enrolled erted CRP were 22-25 enrolled and converted Semi-arid climate: Avg. annual temperature :16 C Avg. annual PPT : 475mm Soil: Amarillo fine sandy loam ph: 7.6 (0-30cm) SOM: 1.4% Sand: 71%
0cm Converted CRP change percent (%) Reference line is CRP Labile OM MBC Specific Metabolic Activities -C POM-N MBC α-galac/ MBC β-gluc/ MBC β-glm/ MBC qco 2 22.7 23.2-3.8-26.8-22.4 111.7-56.8 5.9 31.0 6.1-53.9-38.5-9.1 125.6 46.6 14.2 27.5
33 Gram Total bacteriagram + Actinomyc etes Total fungi Total bacteria Gram AMF Actinomycet es MF Fungi:Bact eria Gram + Total fungi Fungi:Bacter ia
34 ncreased soil organic matter ncreased total microbial biomass Perennial grasses over seeded w/winter annuals Annual corn w/cover crops y = 74.9x - 44.232 R² = 0.73
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